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Introductory Logic	Test #1	March 1, 2006

Name: ________________________	R. Hammack	Score: _________

1. (20 points) Identify each of the following passages as an argument or a non-argument. If the passage is an argument, underline the conclusion.

(a)	If animal experiments were abolished, certain areas of research, such as how to promote recovery of brain damage, would be almost impossible to pursue.

NOT AN ARGUMENT (conditional statement)

(b)	The pencil partially immersed in water appears bent because light is refracted as it travels across the boundary between water and air.

NOT AN ARGUMENT (explanation)

(c)	A mammal is a vertebrate animal that nurses its offspring. Thus, cats and dogs are mammals, as are sheep, monkeys, rabbits and bears.

NOT AN ARGUMENT (illustration)

(d)	A person never becomes truly self-reliant. Even though he deals effectively with things, he is necessarily dependent upon those who have taught him to do so. They have selected the things he is dependent upon and determined the kinds and degrees of dependencies. (B.F. Skinner, Beyond Freedom and Dignity)

ARGUMENT

(e)	The Concert of Europe established the principle of collective security and demonstrated that cooperation was possible among the great powers, but it was only partially successful. The great powers often disagreed among themselves and the ideas of liberalism and nationalism spread. (S.L. Spiegal, World Politics in a New Era)

NOT AN ARGUMENT (report)

2. (20 points) Each of the following passages is an argument. Underline the conclusion. Say if the argument is deductive, inductive, valid, invalid, weak, strong, and (if possible) sound, unsound, cogent, or uncogent.

(a)

Anyone born in the 18^th century is still alive today. Therefore, since George Washington was born in the 18^th century, he is still alive today.

DEDUCTIVE, VALID, UNSOUND

(b)

No one born in the 18^th century is still alive today. Therefore, since George Washington was born in the 18^th century, he is not alive today.

DEDUCTIVE, VALID, SOUND

(c)

An email message informed me that I had won a million dollars, and all I had to do was give them my bank account number for the transfer. I gave them the number, so now I'm rich.

INDUCTIVE, WEAK, UNCOGENT

(d)

No dogs are cats and no cats are fish. Therefore no dogs are fish.

DEDUCTIVE, INVALID, UNSOUND

(e)

Iraq is experiencing political and relegious unrest because the New York Times reports that this is the case.

INDUCTIVE, STRONG, COGENT

3. (12 points) Translate each of the following statements into standard-form categorical propositions.

(a)

Any bank that makes too many risky loans will fail.

All banks that make too many risky loans are banks that will fail.

(b)

If it's a halogen, then it's not chemically inert.

All things that are halogens are things that are not chemically inert.

OR

No things that are halogens are things that are chemically inert.

(c)

Physicists do not understand the operation of superconductors.

No physicists are people who understand the operation of superconductors.

All physicists are people who don't understand the operation of superconductors.

4. (14 points) Use the counterexample method to prove each of the following arguments is invalid.

(a)

If stock prices are rising, then bond prices are falling.
Bond prices are falling.
Therefore stock prices are rising.

Argument Form:

If S, then B.
B
Thus, S

Substitution Instance:

S = "G.Washington was hanged"
B = "G.Washington died"

If G.Washington was hanged, then G.Washington died. (T)
G.Washington died. (T)
Thus, G.Washington was hanged. (F)

Since the argument can be transformed to one with true premises and false conclusion, then it is INVALID.

(b)

Some farm workers are not persons who are paid decent wages, because no illegal aliens are persons who are paid decent wages, and some illegal aliens are not farm workers.

Argument Form:

No I are P.
Some I are not F.
Thus, some F are not P.

Substitution Instance:

I = "cars"
F = "cats"
P = "animals"

No cars are animals. (T)
Some cars are not cats. (T)
Thus, some cats are not animals. (F)

Since the argument can be transformed to one with true premises and false conclusion, then it is INVALID.

5. (6 points) Diagram the following extended argument.

	(1) Government mandates for zero-emission vehicles won't work because (2) only electric cars qualify as zero-emission vehicles, and (3) electric cars won't sell. (4) They are too expensive, (5) their range of operation is too limited, and (6) recharging facilities are not generally available.

For a solution, please see the example at the bottom of page 61 of the text.

6. (14 points) Decide if the following immediate inferences are valid or invalid. Use either Venn diagrams or the Modern Square of Opposition.

(a)

It is false that no Jazz musicians are natives of New Orleans.
Therefore some Jazz muscians are not natives of New Orleans.

Premise says it's false that

[Graphics:HTMLFiles/S06T1diagrams_1.gif]

which means

[Graphics:HTMLFiles/S06T1diagrams_2.gif]

Conclusion says

[Graphics:HTMLFiles/S06T1diagrams_3.gif]

Thus, the argument is INVALID
because the premise and conclusion say different things.

(b)

It is false that all cars are antiques.
Therefore, it is false that some cars are not antiques.

Premise says it's false that

[Graphics:HTMLFiles/S06T1diagrams_4.gif]

which means

[Graphics:HTMLFiles/S06T1diagrams_5.gif]

Conclusion says it's false that

which means

The argument is INVALID because the premise and conclusion are saying different things.

7. (14 points) Use Venn Diagrams to decide if the following arguments are valid or invalid.

(a)

All X are Y.
Some Z are not X.
Thus some Y are Z.

Here is the Venn diagram for the premises:
Here is the Venn diagram for theConclusion:

The argument is INVALID because the premises do not imply the conclusion.

(b)

No A are B.
All C are A.
Thus, no B are C.

Here is the Venn diagram for the premises:
Here is the Venn diagram for theConclusion:

The argument is VALID because the premises imply the conclusion.